DISQUS - Disqus is a global comment system that improves discussion on websites and connects conversations across the web.
Hyvor Talk - The Best Commenting Platform For Your Website
Commento - A fast, bloat-free comments system to foster discussion on your website
Commentbox - Commentbox is a jsf component that allows quick realization of a comment functionality
JustComments - Easy to set up, ad-free and reliable comment system
HTML Comment Box - HTML Comment Box widget for your website. Copy the HTML code and it just works!